Axial flow turbine type rotor machine for elastic fluid operation

ABSTRACT

An axial flow turbine machine intended for elastic fluid operation is provided which includes a rotor with two or more sections each carrying an array of radially directed drive blades, and a stator having a number of fluid inlet nozzles and one or more sections each carrying a circumferential array of guide vanes for directing motive fluid onto the drive blades. A rotor flow path is formed between every two adjacent drive blades in each rotor section and a stator flow path is formed between every two adjacent guide vanes in each stator section. A widened section is provided between the entrance section and the exit section of each rotor section flow path and each stator section flow path, such that the radial distance between the inner flow path defining surface and the outer flow path defining surface is larger in the widened section than in the exit section.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. National Phase Application under 35 U.S.C.371 of International Application No. PCT/SE00/02151 filed Nov. 1, 2000.

BACKGROUND OF THE INVENTION

The invention relates to an axial flow turbine type rotor machine whichis intended for elastic fluid operation. The turbine type machineincludes a rotor having one or more axially spaced sections eachcomprising a circumferential array of radially extending drive blades,and a stator having two or more axially spaced sections each comprisinga circumferential array of radially extending guide vanes. Each one ofthe stator sections is located on opposite sides of the rotor sections,and a flow path is formed between every two adjacent drive blades ineach rotor section, and between every two adjacent guide vanes in eachstator section. Each one of the flow paths has a certain length andextends between an entrance region and an exit region.

Turbine type machines of this type, for instance gas turbines of theabove mentioned type, have in general a limited efficiency due to flowlosses in the flow paths of the rotor and the stator. Big gas turbinemotors, having a power output of some thousand kilowatts, often reach amaximum efficiency of above 90%. Mid size gas turbines motors, however,having a power output up to a few hundred kilowatts, reach a maximumefficiency of no more than 85%. This is considered to be too lowefficiency for making gas turbines in this size range interesting forcertain applications.

SUMMARY OF THE INVENTION

It is the main object of the invention to provide and axial flow turbinetype rotor machine for elastic fluid operation, wherein the flow lossesthrough the rotor and stator flow paths are substantially reduced andthe efficiency of the turbine is substantially increased.

Characteristic features as well as further advantages of the inventionwill appear from the following detailed description of preferredembodiments of the invention and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal sectional view through a turbine machineaccording to the invention.

FIG. 2 shows schematically a spread-out view of a number of drive bladesof one rotor section and a number of guide vanes of one stator sectionof the turbine machine shown in FIG. 1.

FIG. 3 shows, on a larger scale, a detail view of one guide vane and onedrive blade of a turbine machine according to one embodiment of theinvention.

FIG. 4 shows a detail view of a drive blade/guide vane arrangement in aturbine machine according to another embodiment of the invention.

FIG. 5 shows a spread-out view of the drive blade/guide vane arrangementshown in FIG. 4.

FIG. 6 shows a drive blade/guide vane arrangement according to stillanother embodiment of the invention.

DETAILED DESCRIPTION

The turbine machine examples described below in detail are suitablemainly as gas turbine motors. Looking first at the example shown FIG. 1,the turbine machine comprises a stator housing 10 and a rotor 11. Thestator housing 10 is of a substantially cylindrical shape and isprovided at one end with a number of gas inlet nozzles 12 communicatingwith a gas inlet 16 and a funnel shaped outlet diffusor 13 at theopposite end. The stator housing 10 is also provided with a number ofguide vanes 14 which are arranged in an annular section 15 and whichform a circumferential array. The guide vanes 14 are mounted on an innerring structure 17 and are supported by their outer ends against asubstantially cylindrical surface 18 of the stator housing 10. The ringstructure 17 is received in a peripheral space 19 in the rotor 11 and isarranged to co-operate with a cylindrical waist portion 20 on the rotor11 to form a seal.

The rotor 11 comprises a forward part 22 and a rear part 23 and isjournalled relative to the stator housing 10 by two bearings which arenot illustrated. The rotor 11 comprises two axially spaced operatingsections 26, 27 each carrying a circumferential array of drive blades24. The two operating sections 26, 27 are separated by the annularstator section 15. An inner surface 28 formed by the rotor operatingsections 26,27 as well as by the stator ring 17 tapers slowly towardsthe outlet diffusor 13 so as to make the gas flow expand as it passesthrough the turbine.

As shown in FIG. 2, between two adjacent guide vanes 14 in each arraythere is formed a stator flow path 29 having an entrance region A with adistance S_(A) between adjacent guide vanes 14 and an exit region B witha distance S_(B) between the guide vanes 14. Both distances S_(A) andS_(B) are measured transversely to the stator flow path 29. As clearlyillustrated in FIG. 2, the distance S_(A) is considerably larger thandistance S_(B), which means that the cross sectional area of the statorflow path 29 generally decreases from the entrance region A to the exitregion B.

In a similar way, two adjacent drive blades 24 in each array define arotor flow path 30 in which the width S_(C) at the entrance region C islarger than the width S_(D) at the exit region D, which means that eachrotor flow path 30 has a decreasing cross sectional area towards theexit region D.

As illustrated in FIG. 3, the rotor flow path 30 comprises a radiallywidened region F located between the entrance region C and the exitregion D. In the described example, this widened region F is formed by aconcave portion 31 in the inner surface 28. In this widened region F theradial extent R_(F) of the drive blade 24 is larger than the radialextent R_(D) of the drive blade 24 in the exit region D. This means thatthe cross sectional area of the flow path 29 is kept up in size close tothe exit region D, which results in a lower gas velocity upstream of theexit region D and, hence, lower flow losses in the flow path 30.

A similar arrangement is provided in each stator flow path 29 where aconcave portion 32 is located in the ring structure 17 between theentrance region A and the exit region B and forms a widened region E.The radial extent of the guide vane 14 is larger in the widened region Ethan in the exit region B. It should be observed that the ring structure17 is received in the waist portion 20 of the rotor 11.

In FIG. 3, it is clearly shown that the concave portion 31 in the rotor11 forms a radially widened region F in which the radial extent R_(F) ofthe drive blade 24 is larger than the radial extent R_(D) in the exitregion D. The radial extent R_(C) in the entrance region C is evensmaller than the radial extent R_(D) in the exit region D.

The arrangement of radially widened regions E and F in the stator flowpaths 29 and rotor flow paths 30, respectively, are effective in keepingdown the fluid flow velocity through the flow paths 29,30 and, thereby,the flow losses. The radial extent of the drive blades 24 and the guidevanes 14 should be at least 5% larger in the widened regions E, F thanin the exit regions B, D of the flow paths 29, 30 for obtaining apositive effect. In order to get a significant increase of the turbineefficiency, though, the difference in radial extent should beconsiderably larger than that.

However, the percentage of increase of the drive blade/guide vane radialextent in the widened regions depends on the relationship between theradial extent and the length of the respective drive blade or guidevane, such that a drive blade or guide vane having a short length but alarge radial extent must be combined with a relatively smaller concaveportion so as to avoid too large and abrupt area changes of the flowpaths.

Employment of radially widened flow path regions according to theinvention is particularly beneficial in turbines having drive blades andguide vanes with a small radial extent and a considerable length. Insuch turbines the radial extent of the drive blades and guide vanes inthe widened regions may be 10-20% larger than the radial extent of thedrive blades and guide vanes in the exit regions.

According to the invention, the radially widened regions of the flowpaths through the rotor sections as well as the stator sections shallextend over at least 60%, preferably 80% of the flow path length, suchthat the fluid flow velocity is kept down during the main part of theflow path length. A low flow velocity gives low internal flow losses. Atthe very end of the flow paths, there is a reduction in cross sectionalarea which results in a rapid acceleration of the fluid flow.

In order to further reduce the internal flow losses and increase theefficiency of the turbine machine, the embodiment of the invention shownin FIGS. 4, 5 and 6 comprises a drive blade/guide vane arrangement whichemploys radially widened regions between the flow path entrance regionsand exit regions. In this embodiment overlapping between the statorsections and the rotor sections is an essential part of the flow lossreduction.

In the embodiment of the invention illustrated in FIGS. 4 and 5, thereare shown two stator sections with arrays of guide vanes 54, and onerotor section with an array of drive blades 64. Between two adjacentguide vanes 54 there is a stator fluid flow path 59 which has anentrance region A and an exit region B, and between adjacent driveblades 64 there are rotor flow paths 60 each having an entrance region Cand an exit region D. Between the entrance region A and exit region B ofeach stator flow path 59 there is a radially widened region E, andbetween the entrance region C and the exit region D of each rotor flowpath 60 there is a radially widened region F.

As in the previously described example, the distances between adjacentguide vanes 54 are characterized by a relatively large distance S_(A) inthe entrance region A and a relatively small distance S_(B) in the exitregion B. The distance between the guide vanes 54 decreases successivelyalong the stator flow path 59, but due to an increased radial extent ofthe guide vanes 54 in the widened region E the cross sectional area ofthe flow path is kept up in size to a point close to the exit region B.Accordingly, each guide vane 54 has radial extent R_(E) in the widenedregion E which is larger than the radial extent R_(B) in the exit regionB.

In a similar way, the distance between adjacent drive blades 64decreases successively from a large distance S_(C) in the entranceregion C to a small distance S_(D) in the exit region D. The radialdistance R_(F) in the widened region F, however, is larger than theradial distance R_(D) in the exit region D, which means that the crosssectional area of the rotor flow path 60 is kept up in size in the flowdirection to a point close to the exit region D. This means in turn thatthe flow velocity is kept low during the main part of the rotor flowpath 60 and is accelerated over a very short distance in the exit regionD.

As described above in connection with the previous embodiment of theinvention, the inner boundary of the flow paths through the stator endthe rotor sections is defined by an inner surface 28. This inner surface28 is formed by the rotor operating sections 26,27 and by the statorsection or sections 15 together.

A characterising feature of the stator and rotor sections according tothis embodiment of the invention is that trailing end portions 62 of thedrive blades 64 and trailing end portions 52 of the guide vanes 54 areextended in the flow direction beyond those parts of the stator androtor sections that form parts of the inner flow path defining surface28. Moreover, the leading edges of the drive blades 64 as well as theleading edges of the guide vanes 54 are retracted in the flow directiona certain axial distance from the edge of the stator and rotor sections,respectively. An annular neck portion 65 on each rotor section and anannular neck portion 55 on each stator section is formed thereby. Theseannular neck portions 65, 55 on the stator sections and rotor sections,respectively, extend axially in the direction opposite the flowdirection. And the extended trailing end portions 62 and 52 of the driveblades 64 and the guide vanes 54, respectively, extend over the annularneck portions 55,65 of the downstream stator or rotor sections.

This arrangement of the extended trailing portions of the drive blades64 and the guide vanes 54 in co-operation with the annular neck portions65, 55 of the stator and rotor sections, respectively, serves to furtherlower the flow resistance through the flow paths and to improve theefficiency of the turbine.

As appears from FIG. 4, the portion of the inner surface 28 that isformed by a rotor section comprises a convex portion 68 followed in flowdirection by a concave portion 69, wherein the convex portion 68 ispartly formed by the annular neck portion 65. In a similar way, each oneof the stator section parts of the inner surface 28 comprises a convexportion 58 and a concave portion 57, wherein the convex portion 53 ispartly formed by the annular neck portion 55.

FIG. 4 also illustrates that in this embodiment of the invention theouter surface 18 which defines the flow paths 29, 30 is substantiallycylindrical in shape, which means that all variations in the crosssectional areas of the flow paths are accomplished by the convex andconcave portions on stator and rotor section parts of the inner surface28.

FIG. 6 shows an alternative design of the inner and outer flow pathdefining surfaces 18, 28. Instead of locating all of the convex andconcave portions on the inner surface 28, the outer surface 18 of thisalternative is formed with convex and concave portions 86, 87, 88, 89which are located opposite the convex and concave portions 58, 57, 68,69 on the inner surface 28. By this arrangement further possibilitiesare obtained to give the flow paths optimum shapes in order to improvethe fluid flow characteristics through the turbine.

Still an alternative design would be to have cylindrical inner surface18 and locating all of the convex and concave portions 58, 57, 68, 69 onthe outer surface 18.

What is claimed is:
 1. An axial flow turbine type rotor machine forelastic fluid operation, comprising: a rotor having at least one axiallyspaced section, wherein each rotor section comprises a circumferentialarray of radially extending drive blades, a stator having at least twoaxially spaced sections, wherein each stator section comprises acircumferential array of radially extending guide vanes, and each one ofsaid stator sections is located on opposite sides of a respective one ofsaid at least one rotor section, wherein a rotor section flow path isformed between every two adjacent drive blades in each rotor section,and said each rotor flow path has a certain length, a rotor sectionentrance region, and a rotor section exit region, wherein a statorsection flow path is formed between every two adjacent guide vanes ineach said stator section, and said each stator flow path has a certainlength, a stator section entrance region, and a stator section exitregion, wherein in each said rotor section flow path said rotor sectionentrance region has a larger cross sectional area than said rotorsection exit region, and in each said stator section flow path saidstator section entrance region has a larger cross sectional area thansaid stator section exit region, wherein each said stator section flowpath has a substantially constant cross sectional area downstream fromsaid rotor section entrance region over at least 60% of said statorsection flow path length, and wherein each said rotor section flow pathhas a substantially constant cross sectional area downstream from saidrotor section entrance region over at least 60% of said rotor sectionflow path length.
 2. The turbine machine according to claim 1, whereinsaid constant cross sectional area of each said stator section flow pathextends over at least 80% of said stator section flow path length, andsaid constant cross sectional area of each said rotor section flow pathextends over at least 80% of said rotor section flow path length.
 3. Anaxial flow turbine type rotor machine for elastic fluid operation,comprising: a rotor having at least one axially spaced section, whereineach rotor section comprises a circumferential array of radiallyextending drive blades, a stator having at least two axially spacedsections, wherein each stator section comprises a circumferential arrayof radially extending guide vanes, and each one of said stator sectionsis located on opposite sides of a respective one of said at least onerotor section, wherein a rotor section flow path is formed between everytwo adjacent drive blades in each rotor section, and each said rotorflow path has a certain length, a rotor section entrance region, and arotor section exit region, wherein a stator section flow path is formedbetween every two adjacent guide vanes in each said stator section, andeach said stator flow path has a certain length, a stator sectionentrance region, and a stator section exit region, wherein in each saidrotor section flow path said rotor section entrance region has a largercross sectional area than said rotor section exit region, and in eachsaid stator section flow path said stator section entrance region has alarger cross sectional area than said stator section exit region,wherein each said rotor section flow path has a substantially constantcross sectional area downstream from said rotor section entrance regionover at least 75% of said rotor section flow path length, and whereineach said stator section flow path has a substantially constant crosssectional area downstream from said stator section entrance region overat least 75% of said stator section flow path length.
 4. The turbinemachine according to claim 1, wherein said drive blades and said guidevanes extend radially between a substantially rotationally symmetricinner surface and a substantially rotationally symmetric outer surface,wherein each one of said rotor section flow paths has a radially widenedregion located between said entrance region and said exit region, andeach one of said drive blades has a radial extent in said widened regionthat is larger than a radial extent of said drive blade in said exitregion, and wherein each one of said stator section flow paths has aradially widened region located between said entrance region and saidexit region, and each one of said guide vanes has a radial extent insaid widened region that is larger than a radial extent of said guidevane in said exit region.
 5. The turbine machine according to claim 4,wherein a part of said inner surface is formed by said rotor sectionsand a part of said inner surface is formed by said stator sections,wherein a trailing part of each said drive blade in each one of saidrotor sections extends beyond, in a fluid flow direction, the part ofsaid inner surface which is formed by the rotor sections, and the partof said inner surface formed by the stator sections extends beyond saidguide vanes in a direction opposite the fluid flow direction, therebyforming an annular stator section neck portion on the respective statorsections, wherein said trailing part of each said drive blade in one ofsaid rotor sections extends over said stator section neck portion of afollowing stator section in the fluid flow direction, wherein a trailingpart of each said guide vane in each one of said stator sections extendsaxially beyond, in the fluid flow direction, the part of said innersurface formed by the stator sections, and the part of said innersurface formed by rotor sections extends beyond said drive blades in thedirection opposite the fluid flow direction, thereby forming an annularneck portion on the respective rotor sections wherein said trailingparts of said guide vanes in one of said stator sections extend oversaid rotor section neck portion of a following rotor section in thefluid flow direction.
 6. The turbine machine according to claim 5,wherein said exit region of each one of said rotor flow paths is formedby said trailing parts of two adjacent drive blades, and said exitregion of each one of said stator flow paths is formed by said trailingparts of two adjacent guide vanes.
 7. The turbine machine according toclaim 5, wherein on each said rotor section said inner surface comprisesa convex portion followed in the fluid flow direction by a concaveportion, and said convex portion extends beyond said drive blades in adirection opposite the fluid flow direction, thereby forming said rotorsection neck portion.
 8. The turbine machine according to claim 5,wherein on each said stator section said inner surface has a convexportion followed in the fluid flow direction by a concave portion, andsaid convex portion extends beyond said guide vanes in the directionopposite the fluid flow direction, thereby forming said stator sectionneck portion.
 9. The turbine machine according to any one of claims 4-8,wherein said outer surface is formed with at least two annular rotorflow regions each axially coinciding with one of said rotor sections,and wherein each one of said rotor flow regions comprises a convexportion followed in the fluid flow direction by a concave portion. 10.The turbine machine according to any one of claims 4-8, wherein saidouter surface is formed with at least one annular stator flow regioneach coinciding with one of said stator sections, and wherein each oneof said stator flow regions comprises a convex portion followed in thefluid flow direction by a concave portion.
 11. The turbine machineaccording to any one of claims 1-8, wherein each said drive blade has amaximum radial extent which is not more than the length of each saiddrive blade in the fluid flow direction.
 12. The turbine machineaccording to any one of claims 1-8, wherein each said guide vane has amaximum radial extent which is not more than the length of each saidguide vane in the fluid flow direction.